One of the ethical issues of running a RCT on a salvage...

One of the ethical issues of running a RCT on a salvage treatment (particularly if you think your treatment achieves 60%+ survival) is that the placebo arm will see 70-80% death rates within 30 days.
These groups are likely already receiving stem cells under EAP, so effectively you are saying the only way to get the FDA to approve is to reduce access to what is a life saving treatment by half and watch them die.
It will also mean that the trial will need to enrol roughly double the size of what SI is proposing. I think it will be very difficult to convince the academic centers of excellence that treat these patients to participate in an RCT, since the outcomes are so dire.

While I agree that SI’s approach does not meet the FDA requirement of a RCT, perhaps he plans to get FDA sign off on this rescue cohort and the historical survival rates under non-stem SOC.

If he can’t get an iron clad sign off from FDA on approach then this isn’t worth doing.
It might mean that an RCT would need to be conducted on a wider cohort rather than the end stage rescue cohort that SI envisaged, though this would be bigger, longer and more expensive.